Transposed split of ion cut materials

ABSTRACT

A method for the transposed splitting of ion cut materials. Acceptor centers are formed and selectively introduced into a solid material. In addition, atoms are introduced into the solid material at a location that is offset spatially from acceptor centers. The atoms introduced into the solid material are then transported to the location of the acceptor centers where they will then condense in the region of the acceptor centers. As a result, then any expunged layer that is formed by ion splitting as result of the atoms being introduced into the solid material will follow the contour of the location of the acceptor centers, and will thus be transposed from the initial location of the atoms ;introduced into the solid material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. provisional applicationserial no. 60/114,494 filed on Dec. 31, 1998.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

REFERENCE TO A MICROFICHE APPENDIX

Not Applicable

INCORPORATION BY REFERENCE

The following publications, some of which are identified herein usingthe reference numbers set forth below, are incorporated herein byreference:

1. G. F. Cerofolini, R. Balboni, D. Bisero, F. Corni, S. Frabboni, G.Ottaviani, R. Tonini, R. S. Brusa, A. Zecca, M. Ceschini, G. Giebel, andL. Pavesi, Hydrogen Precipitation in Highly OversaturatedSingle-Crystalline Silicon, Phys. Stat. Sol. (a) 150, 539 (1995).

2. M. Bruel, Silicon on Insulator Material Technology, Electron. Lett.31, 1201 (1995).

3. M. Bruel, Process for the Production of Thin Semiconductor MaterialFilms, U.S. Pat. No. 5,374,564 (filed Sept. 15, 1992, issued Dec. 20,1994).

4. X. Lu, S. S. K. lyer, J. Min. Z. Fan, J. B. Liu, P. K. Chu, C. Hu,and N. W. Chueng, Proc. 1996 IEEE Int. SOI Conf. 96CH35937, 48 (1996).

5. Tohru Hara, Takayuki Onda, Yasuo Kakizaki, Sotaro Oshima, TairaKltamura, Kenji Kajiyama, Tomoaki Yoneda, Kohei Sekine and Morio Inoue,Delaminations of Thin Layers by High Dose Hydrogen Ion Implantation inSilicon, J. Electrochem. Soc. Vol. 143, No. 8, August 1996L166-L168.

6. L. B. Freund, A lower bound on implant density to induce wafersplitting in forming compliant substrate structures, AppI. Phys. Left.70 (26), Jun. 30, 1997.

7. Q.-Y. Tong, K. Gutjahr, S. Hopfe, and U. Goesele and T.-H. Lee, Layersplitting process in hydrogen-implanted Si, Ge, SiC, and diamondsubstrates, AppI. Phys. Lett. 70, (11), Mar. 17, 1997 pp 1390-1392.

8. Rober w Bower, Yang A. Li and Yong Jian Chin, The Hydrogen Ion CutTechnology Combined With Low Temperature Direct Bonding, Proceedings ofSPIE, Vol. 3184, pp 2-4, June 1997,

9. Y. Albert Li and Robert W. Bower, Surface Conditions and Morphologyof Hydrogen Ion Cut Low Temperature Bonded Thin Film Layers, SubmittedJJAP.

10. Q.-Y. Tong, T.-H. Lee, L.-J. Huang, Y.-L. Chao and U. Goesele, LowTemperature Si LayerSplitting, Proceedings 1977 IEEE International SOIConference, Oct. 1997 pp 126-127.

11. Aditya Agarwal, T. E. Haynes, V. C. Venezia, D. J. Eaglesham, M. K.Weldon, Y.

12. J. Chabal, and O. W. Holland, Efficient Production ofSilicon-on-Insulator Films by Co-implantation of He⁺with H⁺, Proceeding1977 IEEE International SOI Conference, Oct. 1997 pp 44-45.

12. J. L. Zeigler and J. P. Biersack, The Stopping and Range of Ions inSolids,Trim 95, Pergamon Press (1985) ISBN-0-08-021603-X.

13. A. D. Marwick, G. S. Oehrlein, and M. Wittmer, High hydrogenconcentrations produced by segregation into pt layers in silicon, Appl.Phys. Left. 59 (2), Jul. 8 1991, pp 198-200.

14. Robert W. Bower, Louis LeBoeuf and Y. Albert Li, “TransposedSplitting of Silicon Implanted with Spatially Offset Distributions ofHydrogen and Boron”. II Nuovo Cimento, Vol. 19 D, N. 12, pp 1871-1873,Jan. 1, 1998.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention pertains generally to introducing atoms into solidmaterials, and more particularly to forming and selectively introducingacceptor centers into a solid material and introducing atoms into thesolid material wherein the location of the major concentration of theacceptor centers is offset spatially from the introduced atoms in thesolid material.

2. Description of the Background Art

In recent years, it has been observed that atoms introduced into solidmaterials can result in a thin layer of the material being expunged fromthe solid material when a stiffener is attached to the solid materialand a suitable stress is created to cause the layer crack and break off[1,2,3]. It has been found that the thickness of the expunged layer isvery near that of the mean penetration depth of the introduced ions orthe nearby damage peak created by the introduced ions, when theintroduced ions are ion implanted into the solid material. It has alsobeen observed that atoms that act as acceptor centers in semiconductormaterials tend to attract and condense injected ions near the acceptorcenters location in the material.

There has also been considerable interest in high dose hydrogen ionimplantation into silicon. A recent review article describes a wealth ofbasic physical theory and experiments related to hydrogen implantedsilicon [1]. Bruel first described the Smart Cut® technique that leadsto silicon-on-insulator, SOI, material for use in silicon microcircuits[2,3]. Since that time a number of authors have described and haveproposed theories to quantify the hydrogen bubble generation and crackphenomena that in combination with direct bonding leads to SOI formation[4,5,6]. Recent publications have described variations on Bruel's work.Tong et al. have described layer splitting with ion implanted hydrogenin Ge, SiC, GaAs and diamond [7]. Bower et al. have demonstrated thatlow temperature bonding may be used with hydrogen ion implantation toproduce SOI with a bonding temperature of 200° C. and a splittemperature of 400° C. [8,9]. Tong et al. have shown that boron andhydrogen when implanted to the same projected range allow opticallyobservable surface blisters to be produced with heat treatments of 200°C. for approximately 100 minutes [10]. Agarwal et al. have demonstratedthat the hydrogen ion dose may be reduced from 5×10¹⁶/cm² to 1×10¹⁶/cm²when silicon is also implanted with Helium also at a dose of 1×10¹⁶/cm²[11].

BRIEF SUMMARY OF THE INVENTION

The present invention generally comprises the steps of forming andselectively introducing acceptor centers into a solid material and thenintroducing atoms into the solid material wherein the location of themajor concentration of the acceptor centers is offset spatially from theintroduced atoms in the solid material. When these steps are carried outso that the atoms introduced into the solid material can be transportedin the material, then the introduced atoms may be diffused or drifted tothe location of the acceptor centers that have been selectively placedin the material. The introduced atoms will then condense in the regionof the acceptor centers. As a, then any god L expunged layer that formsas a result of the atoms being introduced into the solid material willfollow the contour of the location of the acceptor centers, and willthus be transposed from the initial location of the atoms introducedinto the solid material.

Therefore, this invention allows an expunged layer to be formed andtransferred to a stiffener that is embedded in the material independentof the location of the introduced atoms.

An object of the invention is to expunge a layer of a solid materialalong a contour line defined by acceptor centers formed in the material.

Another object of the invention is to transpose the initial location ofatoms introduced into the solid material to the location of the acceptorcenters prior to expunging a layer of the solid material using theatoms.

Another object of the invention is to ion cut a material in a regionspaced apart from the location where atoms are introduced in thematerial.

Further objects and advantages of the invention will be brought out inthe following portions of the specification, wherein the detaileddescription is for the purpose of fully disclosing preferred embodimentsof the invention without placing limitations thereon.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood by reference to thefollowing drawings which are for illustrative purposes only:

FIG. 1 schematically shows the steps of a method for forming andintroducing acceptor regions in a solid material and injecting atomsinto the material at a location spaced apart from the acceptor regionsaccording to the invention.

FIG. 2 schematically shows the steps of transporting the injected atomsto the location of acceptor regions shown in FIG. 1.

FIG. 3 schematically shows the steps of splitting the material shownalong a contour line following the contour line of the acceptor regionsin FIG. 2 and attaching the expunged layer to a second material.

DETAILED DESCRIPTION OF THE INVENTION

Referring more specifically to the drawings, for illustrative purposesthe present invention is embodied in the process and resulting structuregenerally shown in FIG. 1 through FIG. 3. It will be appreciated thatthe structure may vary as to configuration and as to details of theelements, and that the method may vary as to the specific steps andsequence, without departing from the basic concepts as disclosed herein.

Referring first to FIG. 1, in accordance with the present invention, aconventional getter material such as Boron is used to form andselectively introduce acceptor centers into a solid substrate material10, such as silicon, using conventional techniques. In order to activatethe acceptor sites and reduce any damage associated with theirintroduction, a high temperature rapid thermal anneal of overapproximately 900° C. is conducted for a short period of time such asless than approximately 1 minute. The introduction of these acceptorcenters 12 defines a “getter surface” 14 in the substrate material.Next, an ion implantation step is carried out. Atoms 16, such asHydrogen atoms, are introduced into the substrate material, also usingconventional techniques, such that the location of the majorconcentration of the acceptor centers is offset spatially by therange-energy considerations of the atoms introduced into the substrate.However, the ion implantation is carried out at a temperature highenough to prevent damage that would restrict the mobility of theHydrogen atoms in the substrate material. A temperature greater thanapproximately 300° C. has been found to be sufficient in this regard.

Referring now to FIG. 2, after the foregoing steps are carried out, theatoms introduced into the substrate material can be transported throughthe material. Accordingly, the introduced atoms 16 may then be diffusedor drifted to the location of the acceptor centers 12 that have beenselectively placed in the material. Diffusion may occur automaticallysimply as a result of the conditions of the ion implantation. Or, theatoms can be drifted as a result of either internal or externallyapplied electric or other force fields.

The introduced atoms will then condense in the region of the acceptorcenters. The material can then be split, thereby creating expungedlayers. As a result of the previous steps, any expunged layer that isformed as a result of the atoms being introduced into the solid materialwill follow the contour of the location of the acceptor centers, namelygetter surface 14, and will thus be transposed from the initial locationof the atoms introduced into the solid material to the location of theacceptor centers.

Still another method of introducing and transporting the atoms to theacceptor centers would be to place the substrate material in anenvironment where Hydrogen would be adsorbed into the material and thendiffused or drifted to the location of the activated getters.

Referring now to FIG. 3, the material is now ready for an expunged layer18 to be formed. This expunging step is preferably carried out after thesubstrate material has been attached to a second substrate material 20by bonding or gluing them together. It will be appreciated, however,that the expunged layer 18 could also be formed without bonding orgluing to a second material prior to expungement.

Note that, while the preferred embodiment of the method is to introducethe getter material prior to introduction of the atoms, the gettermaterial could be introduced after introduction of the atoms as well.

EXAMPLE 1

Boron was implanted into (100) single crystal silicon at an energy of100 KeV, at a temperature above 300° C. with a dose of 1×10¹⁵/cm². Trim95 predicts a mean penetration Rp≈306 nm and vertical stragglingΔRp≈66.7 nm for this implanted boron [12]. The sample was then rapidthermal annealed at 950° C. for 15 seconds. The sample was thenimplanted with H⁺at 40 KeV with a dose of 5×10¹⁶/cm². In this case, Trim95 predicts a mean penetration Rp≈457 nm and vertical stragglingΔRp≈87.3 nm for this implanted hydrogen [12]. The samples were thensubjected to isochronal anneals for ten minutes at 100° C., 200° C.,300° C. and 350° C. Blistering occurred in the samples heated to 300° C.and 350° C. A small sliver split off the surface of the sample heated to300° C. that allowed a measurement of the thickness of the expungedsurface layer. The thickness of this expunged surface layer is found bythis measurement to be 330±15 nm. This clearly indicates that the crackoccurs within experimental error near the projected range, Rp, of theimplanted boron acceptor centers, and far from the Rp of theconsiderably deeper hydrogen implantation of the introduced atoms intothe solid material.

EXAMPLE 2

The experimental evidence strongly suggests that the high dose implantedhydrogen into silicon migrates and accumulates in the region of thelower dose boron distribution where it blisters and cracks the siliconnear the peak of the boron profile. The blister and crack time andtemperature is consistent the results found by Tong et al in theirexperiments with boron and hydrogen implanted to the same peak depth[10]. While the migration of the hydrogen to the boron peak isreminiscent of the work of Marwick where Ga in silicon is found toattract hydrogen implanted into silicon [13]. The Marwick paper suggeststhat ionized Ga⁻ in silicon attracts H⁺ ions and at temperatures of˜200° C. may attract quantities of H much in excess of the density of Gapresent by the reaction:

(HGa)⁰+e⁻+n H⁰→Ga^(″)+(n+1) H⁰  (1)

EXAMPLE 3

Ionized boron may attract and accumulate hydrogen in much the samemanner in our work. Equation (1) does not explain where the accumulatedhydrogen would reside, but other literature suggests that it mightcluster near the Ga or B or perhaps in silicon defect structures thatwould be present after an implantation near these acceptor sites [1,13].The importance of the RTA of the boron in our experiments is not known,but may be important in the light of the ionized donor argument justdescribed, since without the RTA the boron would not be expected to beelectrically active and act as an ionized acceptor.

Accordingly, it will be seen that this invention provides for thetransposition of an ion cut layer in a substrate material by using agetter to form a surface within a substrate material toward whichinjected atoms can be migrated prior to splitting the material. It willbe understood by those skilled in the art that this migration does notoccur automatically, and that energy must be introduced in order tocause the migration. Additional energy is required to cause the materialto expunge along the surface defined by the injected atoms in thevicinity of the getter material. Since the technology for forming theexpunged layers, applying energy to the materials, avoiding damage ofintroduced atoms, introducing and forming acceptors, and introducingatoms are all contained in the current literature and can be practicedby one of ordinary skill in the applied materials area, such technologywill not be described in detail herein.

It will be appreciated that the foregoing method described herein canhave many applications and employ various materials. By way of example,and not of limitation, the atoms injected can be hydrogen atoms, thesubstrate can be a semiconductor such as silicon, the getter material ina silicon substrate can be a Group Ill material such as gallium orboron, the second substrate can be a semiconductor to which a siliconexpunged layer could be bonded or a flexible membrane to which theexpunged layer is glued, and the energy applied can be mechanical energyor heat. Although the description above contains many specificities,these should not be construed as limiting the scope of the invention butas merely providing illustrations of some of the presently preferredembodiments of this invention. Thus the scope of this invention shouldbe determined by the appended claims and their legal equivalents.

What is claimed is:
 1. A method for transposed splitting of ion cutmaterials, comprising the steps of: (a) introducing a plurality ofacceptor centers into a solid material; (b) introducing a plurality ofatoms into said material at a location spaced apart from the location ofsaid acceptor centers; (c) transporting said atoms toward said acceptorcenters; and (d) expunging a layer of said material, wherein saidexpunged layer has a surface with a contour defined by said acceptorcenters.
 2. A method as recited in claim 1, further comprising the stepof attaching said expunged layer to a second solid material.
 3. A methodas recited in claim 1, wherein said solid material is attached to asecond solid material prior to said expunging step.
 4. A method asrecited in claim 1, wherein said solid material comprises asemiconductor material.
 5. A method as recited in claim 4, wherein saidsemiconductor material comprises silicon.
 6. A method as recited inclaim 1, wherein said atoms comprise hydrogen toms.
 7. A method asrecited in claim 1, wherein said acceptor centers are formed byintroducing a getter material into said solid material.
 8. A method asrecited in claim 7, wherein said solid material comprises silicon andsaid getter material is selected from the group consisting of Group IIImaterials.
 9. A method as recited in claim 7, wherein said solidmaterial comprises silicon and said getter material is selected from thegroup consisting of gallium and boron.
 10. A method as recited in claim1, wherein said atoms are transported by rift created by a force field.11. A method as recited in claim 1, wherein said atoms are transportedby drift created by an electric field.
 12. A method as recited in claim1, wherein said atoms are transported by diffusion.
 13. A method fortransposed splitting of ion cut materials, comprising the steps of: (a)introducing a plurality of acceptor centers into a solid material,wherein said acceptor centers form a contour line in said material; (b)introducing a plurality of atoms into said material at a location spacedapart from the location of said acceptor centers; (c) transporting saidatoms toward the location of said acceptor centers; and (d) expunging alayer of said material, wherein said expunged layer has a surface with acontour following the contour line of said acceptor centers.
 14. Amethod as recited in claim 13, further comprising the step of attachingsaid expunged layer to a second solid material.
 15. A method as recitedin claim 13, wherein said solid material is attached to a second solidmaterial prior to said expunging step.
 16. A method as recited in claim13, wherein said solid material comprises a semiconductor material. 17.A method as recited in claim 16, wherein said semiconductor materialcomprises silicon.
 18. A method as recited in claim 13, wherein saidatoms comprise hydrogen atoms.
 19. A method as recited in claim 13,wherein said acceptor centers are formed by introducing a gettermaterial into said solid material.
 20. A method as recited in claim 19,wherein said solid material comprises silicon and said getter materialis selected from the group consisting of Group III materials.
 21. Amethod as recited in claim 19, wherein said solid material comprisessilicon and said getter material is selected from the group consistingof gallium and boron.
 22. A method as recited in claim 13, wherein saidatoms are transported by drift created by a force field.
 23. A method asrecited in claim 13, wherein said atoms are transported by drift createdby an electric field.
 24. A method as recited in claim 13, wherein saidatoms are transported by diffusion.
 25. A method for transposedsplitting of ion cut materials, comprising the steps of: (a) introducinga plurality of acceptor centers into a solid material and forming acontour line in said material defined by said acceptor centers; (b)introducing a plurality of atoms into said material at a location spacedapart from the contour line of said acceptor centers; (c) transportingsaid atoms toward the contour line formed by said acceptor centers; and(d) expunging a layer of said material along a contour line followingthe contour line of said acceptor centers.
 26. A method as recited inclaim 25, further comprising the step of attaching said expunged layerto a second solid material.
 27. A method as recited in claim 25, whereinsaid solid material is attached to a second solid material prior to saidexpunging step.
 28. A method as recited in claim 25, wherein said solidmaterial comprises a semiconductor material.
 29. A method as recited inclaim 28, wherein said semiconductor material comprises silicon.
 30. Amethod as recited in claim 25, wherein said atoms comprise hydrogenatoms.
 31. A method as recited in claim 25, wherein said acceptorcenters are formed by introducing a getter material into said solidmaterial.
 32. A method as recited in claim 31, wherein said solidmaterial comprises silicon and said getter material is selected from thegroup consisting of Group III materials.
 33. A method as recited inclaim 31, wherein said solid material comprises silicon and said gettermaterial is selected from the group consisting of gallium and boron. 34.A method as recited in claim 25, wherein said atoms are transported bydrift created by a force field.
 35. A method as recited in claim 25,wherein said atoms are transported by drift created by an electricfield.
 36. A method as recited in claim 25, wherein said atoms aretransported by diffusion.